Combo Rush allows for you and up to three friends to compete across every level in the game in one of four modes. Here's how Roll7 describes them:
Time: Rack up the beefiest score in a set time.
Race: Clash against your mates in a quick race to the end.
One-Shot: Think Daily Grind, but without the practice!
Score: Set a target score and pray you don't sloppy land that massive combo!
Before starting, you'll set a length for a tournament where each round is scored until you have a winner. Should you end up tied afterward, you'll compete in the skateboarding equivalent of sudden death: a random One-Shot level.
Combo Rush will be available for free today. This update as describes as "one massive, sexy, bodacious update left for you on PS4." The mode had been discussed prior to launch, but didn't end up finished in time.